Maas, Mandy (2014)

Implementation of a Surface Energy Balance Algorithm based on SEBAL for the Estimation of Evapotranspiration in the Tarim River Basin with MODIS Time Series

Irrigated agriculture is a main consumer of global water resources. Therefore, determining the water consumption by crops is important for water resource planning and management. The Tarim River Basin located in northwestern China is characterized by a warm continental arid climate. The combination of increased demand for irrigation water, due to the expansion of farmland, and high evapotranspiration (ET) rates leads to numerous environmental problems. Within this study, a surface energy balance algorithm based on the SEBAL model was applied, to estimate ET of the Tarim River Basin with MODIS satellite imagery and meteorological data. Therefore, a framework was implemented in Java using the open source project BEAM that allows an automatic processing of annual time series. Exemplary, two datasets for the years 2007 and 2010 were prepared. An evaluation with reference ET showed good agreement with modelled results. Seasonal ET of farmland in the Tarim River Basin was estimated in the range of about 800 to 1,200 mm. Preliminary analysis revealed an increase of seasonal ET within agricultural area from 2007 to 2010. Major differences in seasonal ET between large scale and small scale farming systems in the Tarim River Basin were not observed, whereby a relation towards the affected areas showed that large scale systems have a bigger impact on water resources, since these cover a fourfold larger region.